The molding of thermoset polymers is a technologically important processing technique. In one version of this technique, a liquid monomer (e.g., an olefin) and a polymerization catalyst are mixed and poured, cast or injected into a mold. The polymerization proceeds (the article "cures") and on completion the molded part is removed from the mold for any post cure processing that may be required. The polymerization reaction mixture may optionally contain additional ingredients such as modifiers, fillers, reinforcements, and pigments.
The time during which the liquid monomer/catalyst mixture can be worked on after the monomer and catalyst are mixed is called the "pot life" of the polymerization reaction mixture. In general, the ability to control reaction rates increases in importance in the molding of larger parts. To mold successfully, the reaction mixture must not cure so quickly that the liquid monomer/catalyst mixture polymerizes before the mixture can be introduced in to the mold or before the catalyst has had time to completely dissolve. However, for convenience and expedient cycle time, it is also important that the catalyst activate within a reasonable time after the mold is filled.
Reaction Injection Molding ("RIM") has previously been used for the molding of polymer articles using a polymerization catalyst and olefin monomer (U.S. Pat. Nos. 4,400,340 and 4,943,621). In these previous processes, a metal (W or Mo) containing compound is dissolved in a first monomer stream. The monomer streams are then mixed and the metal containing compound and the alkyl aluminum compound react to form an active catalyst which then catalyzes the polymerization reaction. Because the reaction proceeds extremely quickly once the catalyst is formed, any attempt to modulate the polymerization time relies on delaying the formation of the active catalyst species. For example, the alkyl aluminum compound stream typically includes an inhibitor, usually a Lewis base, which suppresses the formation of the catalyst.
As molding processes tackle larger and more complicated polymeric components, there is an increasing need for more reliable systems which can extend pot life and/or control the rate of metathesis polymerization reactions.